Changelog:
-Added command /impossiblemobs
-Added /impossiblemobs enable
Enables the plugin
-Added /impossiblemobs disable
Disables the plugin
-Added /impossiblemobs limitworlds <true/false>
Plugin will only be enabled in enable worlds if true
-Added /impossiblemobs enableworld <world name>
Adds a world to the list of enabled worlds (only works if limitworlds is true)
-Added /impossiblemobs disableworld <world name>
Removes a world from the list of enabled worlds (only works if limitworlds is true)